In spite of wide publicity about health risks, smoking rates in women are at unacceptably high levels. Prevalence rates are declining faster in men than women; if this trend continues, women are expected to surpass men in smoking prevalence by the year 2000. Studies have shown that female subjects have special concerns with weight gain and smoking cessation, and that weight effects due to smoking are greater in women than in men. Further, withdrawal effects from smoking cessation may be more severe in women than men. These factors may explain lower cessation rates and higher relapses in women. Evidence also shows that the menstrual cycle may affect dietary intake and withdrawal symptoms in smoking cessation in women. The purpose of this grant proposal is to look at the effects of the phase of the menstrual cycle on smoking cessation in women, specifically to determine the effect of the phase of cycle on weight gain, caloric intake (including nutrient content) and resting metabolic rate (RMR), as well as on withdrawal symptoms with and without nicotine replacement. The present proposal is divided into 2 parts conducted over 3 years. Part I will look at effects of phase of the menstrual cycle on appetitive behavior and withdrawal symptoms. Subjects will be randomly assigned to either a smoking or nonsmoking group an will be admitted as in-patients for two 7-day periods, counterbalancing the phases of the menstrual cycle. There will be approximately one month between admission. Subjects will be asked to resume smoking during the interim period. During the 2-month period prior to the first hospitalization, weight, blood pressure, premenstrual symptoms, withdrawal symptoms, caloric intake (3-day food records) and ovulation documentation will provide baseline data. On each admission subjects will undergo 2 days of baseline and lib smoking, and 5 days of smoking cessation (if assigned to the nonsmoking group). Assessment of weight, caloric intake, RMR, tobacco withdrawal symptoms and premenstrual symptoms will be done. Part II of the study will examine the effects of the phase of the menstrual cycle on weight gain and withdrawal symptoms in the presence of transdermal nicotine system (TNS). The design is the same as Part I with the exception that all subjects will stop smoking during the two admissions and subjects will randomly be assigned to transdermal nicotine or placebo patch. The results of this research will provide new information which will be important and useful in developing effective strategies for smoking cessation in women.